Ask the RCW Dietitian: Grape Juice and Stomach Bugs


My nutrition question is related to 100% juice. I recently heard from a co-worker that 100% grape juice can impact the pH balance in your gut. Is this true? The benefit would be if you were recently exposed to someone with a stomach bug or you start to feel icky (but not sick yet), drinking grape juice can help you fight off a possible forming ‘bug’ or you’ll possibly be less likely to get it. What are the benefits of drinking 100% juice or concentrate? Should kids avoid this?

Great question! There are a few layers to this one so let’s take them one by one.

Can grape juice change the pH balance in your gut? The short answer is no, or at least not enough to matter. As I discussed in my breakdown of the alkaline diet a few weeks ago, our stomach has a pH of somewhere between 1.5 and 3.5, which is very acidic (the closer the pH is to zero, the more acidic a substance is). This is regulated by our bodies – our stomach needs to be acidic to do its job. The pH of grape juice is unlikely to be lower than 3, and even if it were higher or lower it wouldn’t change the pH of stomach acid in a meaningful way. Besides, the two most common stomach bugs (norovirus and rotavirus) are capable of surviving very acidic environments – which is a major reason they are so effective at making us sick.

Does grape juice have other antiviral or antimicrobial properties? Maybe, but probably not once it’s in our digestive system. Researchers in the 1970’s found that extracts of grapes did inactivate some viruses, but it’s important to remember that these effects happened in a test tube, not in a human body. A test tube allows researchers to easily isolate variables; our bodies are far more complex. Further research found that grape juice was not effective in preventing viral infections in the digestive system. The truth is that no foods will “cure” a stomach bug. There is some evidence that vitamin C and zinc could shorten the duration and decrease severity of a cold; but they are far from a “cure”, and stomach viruses are different than the viruses that cause cold symptoms.

What are the benefits of drinking 100% juice or concentrate? Should kids avoid this? In May, the American Academy of Pediatrics released new recommendations related to fruit juice advising the following:

  • Babies younger than one year should not have juice at all.

  • 1-3 year olds should be limited to 4 ounces daily, 4-6 ounces for 4 to 6 year-olds.

  • For children aged 6 to 18, a limit of 8 daily ounces of juice is advised.

So fruit juice should generally be avoided or limited in young children. Fruit juice can provide some vitamins but will be relatively high in sugar and low in fiber (if there’s any fiber at all). Consider orange juice. Four ounces of orange juice – just half a cup – has about the same number of calories as an entire orange. The whole orange, however, will give you a bit more vitamin C and far more fiber to keep you fuller for longer. If you have the option, go for the whole fruit.

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